Build with Meson or CMake and pass the Oolite version from Git rather than hardcoding

[mcarans]

Build with Meson (which has GNUstep support) or CMake (which I already got working before on Linux) and pass the Oolite version from Git rather than hardcoding.

[oocube]

Is Meson and the version number somehow connected? If not, this issue is better split into two.

[mcarans]

Yes Meson and CMake have built in support for Git versioning. Makefiles require a custom implementation.

Another thing I've noticed is that CLion does not understand the GNUstep makefile. I think it should work much better with either CMake or Meson.